Sender recall

[Gabrics]

I do believe that this could be advantageous in some cases:
after a very long time sender should be able to "call-back" a still unspent UTXO

Our current case:
A customer used Samurai wallet (on our advice ) and backed-up the seed words from the devices as they were ordered (restore was also tested!).
Unfortunately Samurai changed it a while back to mandate a passphrase for new wallets (I believe it was always there, but optional). Which the customer didn't back-up (as we told them to keep the seed words which was true at that time). We weren't aware as we didn't create new wallet in Samurai for a while.
Now they face loss of access to some of their Bitcoins because a phone was lost. They tried to restore from the seed (without the unknown passphrase), but they ended up with different root key hence they see zero balance (they have tried what they could as passphrase).

I don't blame it on Samurai as they clearly state this in the app and you even have to click a checkbox to agree. Still I kind of feel sad and thinking about solutions. I also believe this causes serious blow back for Bitcoin even among those trying to be responsible.
They do know the TXID in question (still unspent) and they do have the private key of the source UTXO.

My thinking is something like this:
After a given time (years) it could be a good option for the sender to be able call back/invalidate a still unspent transaction.

I believe this could help a lot of people to reclaim lost funds. I know this is a big one (maybe a silly too) one and won't be fast if ever happens. Goes a against the basics too, but not so much I believe as if someone want's to avoid this possibility he/she would only need to move the funds and that would make this "re-call" impossible.

Thanks

PS:
Those who have seed words only as backup for Samurai should check if it is enough for successful restore (on a different phone!) while they still have access to the original wallet.

Any idea how long would it take to brute force the passphrase with lets say 6 characters long (and check which one has balance...).

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[HeRetiK]

My thinking is something like this:
After a given time (years) it could be a good option for the sender to be able call back/invalidate a still unspent transaction.

I believe this could help a lot of people to reclaim lost funds. I know this is a big one (maybe a silly too) one and won't be fast if ever happens. Goes a against the basics too, but not so much I believe as if someone want's to avoid this possibility he/she would only need to move the funds and that would make this "re-call" impossible.

Thing is, that would open a whole different can of worms. Now you get people wondering why the coins they bought a couple years back have suddenly vanished (ie. stolen back by prior owners). Now instead of "You should have kept a backup" it's "You should have moved your coins after receiving them". Makes matters kinda worse, don't you think?

Even worse still, that would pretty much break cold storage. The coins you sent to cold storage to hold unto for the next couple of years? Anyone getting access to the hot wallet you used to sent the coins to cold storage is now able to clean out your stash some time further down the road, even if the hot wallet is empty by now.

[bitmover]

Lost funds are not a big problem, as compared to the problems that would show up if your suggestion gets implemented.
I believe the right of  property is one of the biggest pillars of bitcoin. Once you have your privatekey, nobody can take funds from you. Neither the police, the justice, the government, thieves, no one. Not even you, if you lose it. No back door.

[Gabrics]

I understand and kind of have to agree. Ownership does "trump" -and it should- stupid.

We will try to use the older versions mentioned!

Thanks!